Taking the fine-grained sedimentary rocks of the 4th Member of the Yingcheng Formation in the Shuangcheng area of the Songliao Basin as the research object, based on the natural gamma logging data of Well S1 from 1544 to 1710 m, this study identifies the characteristics of Milankovitch cycles using spectral analysis and wavelet transform methods, and discusses the sedimentary response mechanism in combination with geochemical indicators. The research shows that 4 IV-level cycles, 12 V-level cycles, and 30 VI-level cycles can be identified in the study interval. The errors between the cycle thickness ratios and the theoretical Milankovitch cycle ratios are all within 10%, indicating that this sedimentary system is significantly controlled by astronomical orbital cycles. The analysis reveals that it can be further divided into warm-humid climate half-cycles and cold-arid climate half-cycles according to the long eccentricity cycle and sedimentary environment characteristics. In the warm-humid climate half-cycle, the daily sunlight received on the surface is more, the rainfall is abundant, the water salinity tends to be freshwater, the water depth is relatively deep, and the reduction degree is high, with relatively high TOC values at this stage. In the cold-arid climate half-cycle, the daily sunlight received on the surface is less, the rainfall decreases, the water salinity tends to be saltwater, the water depth is relatively shallow, and the reduction degree is weak, with relatively low TOC values at this stage.